NMRCloudQ： a quantum cloud experience on a nuclear magnetic resonance quantum computer

Cloud-based quantum computing is anticipated to be the most useful and reachable form for public users to experience with the power of quantum. As initial attempts, IBM Q has launched influential cloud services on a superconducting quantum processor in 2016, but no other platforms has followed up yet. Here,we report our new cloud quantum computing service – NMRCloud Q(http://nmrcloudq.com/zh-hans/),where nuclear magnetic resonance, one of the pioneer platforms with mature techniques in experimental quantum computing, plays as the role of implementing computing tasks. Our service provides a comprehensive software environment preconfigured with a list of quantum information processing packages,and aims to be freely accessible to either amateurs that look forward to keeping pace with this quantum era or professionals that are interested in carrying out real quantum computing experiments in person. In our current version, four qubits are already usable with in average 99.10% single-qubit gate fidelity and 97.15% two-qubit fidelity via randomized benchmaking tests. Improved control precisions as well as a new seven-qubit processor are also in preparation and will be available later.

Demonstration of an ultra-low-threshold phonon laser with coupled microtoroid resonators in vacuum

We demonstrate an ultra-low-threshold phonon laser using a coupled-microtoroid-cavity system by introducing a novel coupling approach.The scheme exhibits both high optical quality factors and high mechanical quality factors.We have experimentally obtained the mechanical quality factor up to 18,000 in vacuum for a radialbreathing mode of 59.2 MHz.The measured phonon lasing threshold is as low as 1.2μW,which is～5 times lower than the previous result.

Second-order magnetic field gradient-induced strong coupling between nitrogen-vacancy centers and a mechanical oscillator

We consider a cantilever mechanical oscillator(MO) made of diamond. A nitrogen-vacancy(NV) center lies at the end of the cantilever. Two magnetic tips near the NV center induce a strong second-order magnetic field gradient. Under coherent driving of the MO, we find that the coupling between the MO and the NV center is greatly enhanced. We studied how to generate entanglement between the MO and the NV center and realize quantum state transfer between them. We also propose a scheme to generate two-mode squeezing between different MO modes by coupling them to the same NV center. The decoherence and dissipation effects for both the MO and the NV center are numerically calculated using the present parameter values of the experimental configuration. We have achieved high fidelity for entanglement generation, quantum state transfer, and large twomode squeezing.

Why quantum adiabatic computation and D-Wave computers are so attractive?

Because of the possibility that improves our computational capability dramatically,in the past two decades quantum computation has been attracting more and more attentions.Particularly,in recent years remarkable progresses have been made for theoretical researches and experimental implementations in this area,which will probably bring us quantum computer able to beat